BANGOR — Nine of 10 people charged in connection with a cocaine and oxycodone distribution ring allegedly operating in central Maine were arraigned Tuesday in U.S. District Court.

They are among 16 people indicted May 17 by a federal grand jury on charges related to the distribution of cocaine and oxycodone between Jan. 1 and March 17, 2012. The indictment was sealed until 10 of the defendants were arrested Tuesday.

The names of the other six defendants have been redacted. It is the practice of the U.S. attorney’s office to make defendants’ names public as they are arrested.

All are charged with conspiracy to possess with the intent to distribute and conspiracy to distribute oxycodone and 500 grams or more of cocaine, the most serious charge. Five hundred grams equals 17.5 ounces, or more than a pound of cocaine.

McCray also was indicted on two separate distribution counts, one for oxycodone and the other for cocaine.

He first was arrested in March after he allegedly sold oxycodone to a confidential informant. He has been held without bail since his arrest on March 17. McCray on Tuesday agreed to be held without bail on the new charges.

The earlier case, in which McCray was charged with distribution of a mixture or substance containing oxycodone, is unrelated to the new charges, according to the U.S. attorney’s office. McCray has pleaded not guilty to that charge.

Justin Lacroix, Blodgett and Hernandez also were indicted on one count each of possession with intent to distribute cocaine. In addition to that charge, Blodgett and Hernandez were indicted on a charge of possession with intent to distribute oxycodone.

All the defendants but Hanson on Tuesday pleaded not guilty to the charges. He is scheduled to be arraigned Wednesday in federal court in Bangor.

Assistant U.S. Attorney Joel Casey, who is prosecuting the case, has filed motions asking that Justin Lacroix, Jesse Jones, Saul Hernandez and Hanson be held without bail pending the outcome of their cases. Bail hearings before U.S. Magistrate Judge Margaret Kravchuk are scheduled to be held later in the week.

If convicted of the conspiracy charge, each defendant faces a minimum sentence of five years and a maximum sentence of up to 40 years in federal prison, according to the U.S. attorney’s office. The remaining charges each carry a maximum penalty of 20 years imprisonment.

The case was investigated by the U.S. Drug Enforcement Administration, the U.S. Department of Homeland Security’s Office of Homeland Security Investigations, Maine Drug Enforcement Agency, Maine State Police, the police departments of Waterville, Augusta, Fairfield, Oakland and Skowhegan, and the Somerset and Kennebec county sheriff’s offices. The Kennebec and Somerset County district attorney’s offices and the Maine attorney general’s office also provided assistance in the investigation.